Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

An internal combustion piston engine based on a four-stroke process,
including a crankcase in which at least one cylinder/piston assembly is
arranged, the piston being guided by a connecting rod connected to a
crankshaft. At least one cylinder head closes the cylinder, each of whose
intake and exhaust channels are controlled by at least one intake valve
and one exhaust valve (13, 13a). The intake and exhaust valves (13, 13a)
are actuable by a rocker arm (5) or a finger lever driven by a camshaft
(1) through intake and exhaust cams (2). The rocker arms or finger levers
are guided on at least one axle (6). A brake control device is provided
which includes, in the region of the base circle of the exhaust cam (2),
at least one additional cam (1) for an additional opening of at least one
of the exhaust valves (13, 13a). A control element (12, 12a) is installed
between the rocker arm (5) or finger lever and the exhaust valve or
valves (13, 13a), which control element (12, 12a) can be connected to the
pressurized oil circulation system of the internal combustion piston
engine and whose length can be varied, so that the additional cam (3) is
active during a braking operation and inactive during a pure engine
operation. The control element (12) is arranged in a bridge (11) that is
associated with a plurality of exhaust valves (13, 13a).

Claims:

1. An internal combustion piston engine based on a four-stroke process,
comprising a crankcase in which at least one cylinder/piston assembly is
arranged, the piston being guided by a connecting rod connected to a
crankshaft, at least one cylinder head for closing the cylinder, the
intake and exhaust channels of the at least one cylinder are controlled
by at least one intake valve and one exhaust valve, said intake and
exhaust valves being actuable by a rocker arm or a finger lever driven by
a camshaft through intake and exhaust cams, the rocker arms or finger
levers are guided on at least one axle, and a brake control device which
comprises, in a region of a base circle of the exhaust cam, at least one
additional cam for an additional opening of at least one of the exhaust
valves, and in which a control element is installed between the rocker
arm or finger lever and the at least one exhaust valve, the control
element can be connected to a pressurized oil circulation system of the
internal combustion piston engine and has a length that can be varied, so
that the additional cam is active during a braking operation and inactive
during a pure engine operation, the control element is arranged in a
bridge that is associated with a plurality of the exhaust valves.

2. An internal combustion piston engine according to claim 1, wherein the
control element is arranged on one end of the bridge which is associated
with a plurality of the exhaust valves, said control element being
operatively connected to a stem of one of the exhaust valves.

3. An internal combustion piston engine according to claim 1, wherein the
control element is arranged approximately at a central position in the
bridge which is associated with a plurality of the exhaust valves, said
control element being operatively connected to a free end of the rocker
arm or finger lever.

4. An internal combustion piston engine according to claim 1, wherein a
control piston is associated with elements of a hydraulic valve lash
adjusting element, the control piston is loaded on one side by a spring
and can be loaded on another side by pressurized oil and to be brought
into operative connection to a valve body of a non-return valve in an
opening direction.

5. An internal combustion piston engine according claim 1, wherein
transmitting elements between the exhaust cam and the exhaust valves are
loaded by spring force so far in direction towards the exhaust valves
that, during a performance operation of the internal combustion engine,
no contact takes place with the base circle and the additional cam.

Description:

[0001] This application claims the benefit of German Patent Application
No. 102010011454.5, filed Mar. 15, 2010, which is incorporated herein by
reference as if fully set forth.

FIELD OF THE INVENTION

[0002] An internal combustion piston engine based on a four-stroke
process, comprising a crankcase in which at least one cylinder/piston
assembly is arranged, the piston being guided by a connecting rod
connected to a crankshaft, at least one cylinder head for closing the
cylinder, each of whose intake and exhaust channels are controlled by at
least one intake valve and one exhaust valve, said intake and exhaust
valves being actuable by a rocker arm or a finger lever driven by a
camshaft through inlet and exhaust cams, the rocker arms or finger levers
being guided on at least one axle, and further comprising a brake control
device which comprises, in the region of the base circle of the exhaust
cam at least one additional cam for an additional opening of the at least
one exhaust valve, and in which a control element is installed between
the rocker arm or finger lever and the exhaust valve or valves, which
control element can be connected to the pressure oil circulation of the
internal combustion piston engine and whose length can be varied, so that
the additional cam is active during a braking operation and inactive
during a pure engine operation.

BACKGROUND OF THE INVENTION

[0003] A generic internal combustion piston engine of the pre-cited type
is known from U.S. Pat. No. 3,809,033. An actuating piston installed in
the rocker arm of this engine is operatively connected to a bridge
associated to two exhaust valves. The pressure chamber of the actuating
piston is controlled by a control valve, so that oil pressure can be
increased and decreased and the actuating piston can be retracted for the
performance operation of the internal combustion engine or extended for
the braking operation. The additional cam is active in the one case and
inactive in the other.

[0004] A drawback of this configuration is particularly that, due to the
spatial arrangement in the rocker arm, it is only possible to open all
the exhaust valves intermediately at the same time, and this is only
restrictedly desired. Furthermore, this also makes the installation of a
hydraulic lash adjusting element for simplifying maintenance of the
internal combustion engine more difficult.

[0005] Further, an internal combustion piston engine comprising a
compression relief brake device is also known (DE-30 03 566 A1). In this
internal combustion engine, the additional cam is configured as a movable
component that can be pushed into the base circle contour or pushed
outwards out of the base circle contour. For this purpose, the camshaft
has a hollow configuration and comprises an actuating device which
displaces the additional cam. The actuating device must further also
comprise actuating elements outside of the camshaft, through which
actuating elements the inner actuating device is controlled.

[0006] The required structural complexity for extending and retracting the
additional cams is considerably high and cost-intensive and therefore
considered as a drawback.

SUMMARY OF THE INVENTION

[0007] It is therefore the object of the invention to improve an internal
combustion piston engine with the initially described features, so as to
provide an effective engine brake through intermittent opening of even
one out of a plurality of exhaust valves in the region of the upper dead
center of the internal combustion piston engine, which brake must be
realizable through simple measures and low costs. In addition, this
should be accomplished in connection with components of a hydraulic lash
adjusting element.

[0008] The invention achieves the above object by the fact that control
element is arranged in a bridge that is associated to a plurality of
exhaust valves.

[0009] If the control element is arranged at a central position in the
bridge and is operatively connected to the free end of the rocker arm or
finger lever, the control element is active for both exhaust valves.

[0010] If, in contrast, the control element is arranged on one end of the
bridge and is operatively connected only to a stem of one exhaust valve,
the control element is associated only to one exhaust valve.

[0011] In an advantageous development of the invention, the control
element comprises components, known per se, of a of a hydraulic lash
adjusting element. A control piston is associated to the components of
the hydraulic valve lash adjusting element, which control piston is
loaded on one side by a spring and can be loaded on another side by
pressure oil and can therefore be brought into operative connection to
the valve body of a non-return valve of the valve lash adjusting element
in opening direction.

[0012] When the control piston is loaded with reduced oil pressure, the
spring presses the control piston against the valve body of the
non-return valve, which is preferably configured as a ball, and opens
this. As a result, the control element can get shortened, so that the
additional cam is inactive and no compression relief opening of the
exhaust valve or valves takes place. The rocker arm or finger lever, if
necessary also an installed tappet, is in constant contact with the
additional cam. The additional lift, however, is suppressed in this case
by the control element.

[0013] When the control piston is loaded through oil pressure, the
non-return valve can close and a pressure is built up in the hydraulic
valve lash adjusting element. As a result, the high pressure chamber is
formed, the working piston being situated in the extended position, also
through the force of the compression spring. The thus formed high
pressure chamber causes the activation of the additional cam which leads
to a switching-on of the engine brake.

[0014] During the performance operation of the engine, it is also possible
to displace the transmitting elements situated between the exhaust cam
and the exhaust valves so far in a direction towards the exhaust valves,
preferably by spring-loading, that the respective component connected to
the exhaust cam does not come into contact with the base circle and the
additional cam.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] For a further elucidation of the invention reference will be made
to the appended drawings in which examples of embodiment of the invention
are shown in simplified illustrations. The figures show:

[0016] FIG. 1: a side view of a valve train including a sectional view
through a camshaft and an axle for rocker arms, as also a view of exhaust
valves, a bridge and a rocker arm,

[0017] FIG. 2: a sectional view through the exhaust valves, the rocker arm
and the bridge of FIG. 1,

[0018] FIG. 3: a sectional view through a control element corresponding to
FIGS. 1 and 2,

[0019] FIG. 4: a side view of a valve train similar to FIG. 1, with a
modified bridge,

[0020] FIG. 5: a sectional view through exhaust valves, a bridge according
to FIG. 4 and a part of the rocker arm, and

[0021] FIG. 6: a sectional view through a control element of FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] In FIGS. 1 and 6 a camshaft, as far as specifically shown, is
identified at 1, on which camshaft are arranged, among other things,
exhaust cams 2. Additional cams 3 are arranged in the region of the base
circle of the exhaust cams 2 according to FIGS. 1 and 4 and serve for
producing compression relief strokes of one or two exhaust valves. A
rocker arm 5, mounted on an axle 6, is connected through a roller 4 to
the exhaust cams 2. The axle 6 comprises bores 7 and 8 serving for a
pressurized oil supply and a pressure oil discharge. An adjusting screw 9
is screwed onto the further end of the rocker arm 5 and is connected, in
FIG. 2, through a ball socket 10 to a bridge 11 and to a control element
12a in FIG. 4. Bores in the rocker arm 5, in the adjusting screw 9 and in
the ball socket 10 are connected to one of the bores 7 or 8 in the axle 6
and lead, according to FIG. 2, into bores in the bridge 11 which lead to
the control element 12 on one end of the bridge 11. In FIG. 4, the bore
in the ball socket 10 is connected to an oil channel that leads directly
into control element 12a. In FIG. 2, the exhaust valve identified at 13
is supported on the bridge 11, while the exhaust valve identified at 13a
is connected to the control element 12. In FIG. 4 both exhaust valves 13,
13a are supported on the bridge because the control element 12a is
arranged at a central position in the bridge 11.

[0023] The control elements according to FIGS. 3 and 6 have a basically
similar structure. They differ from each other in size and by a
modification of the outer housing. The control element 12 according to
FIG. 3 comprises an outer housing 14 in which a working piston 15 is
inserted. The working piston 15 is supported through a compression spring
16 on a piston 17 of the hydraulic lash adjusting element in which a
non-return valve 18 comprising a ball 19 as a valve body is arranged.
Adjoining the piston 17, which is pressed into the housing 14, 14a, is
arranged a control piston 20 which is loaded by a spring 2 in a direction
towards the non-return valve 18 and can be loaded on the opposite side
through pressure oil which can be fed in a controlled manner from the
axle 6 through different bores. Control valves, not illustrated, are
installed in the pressure oil supply to the control piston 20 and control
the supply flow of the pressure oil and its return flow. Moreover, a leak
oil duct is arranged on the installation space of the spring 21 to
prevent an undesired pressure build-up in this space. The control element
12 differs from the control element 12a in that the outer housing
identified at 14a comprises recesses and turned grooves to assure a
reliable supply flow of pressure oil from the ball socket 10 to the
control piston 20.

[0024] As already mentioned in the general description, when the control
piston 20 is supplied with a reduced oil pressure, the control piston
opens the ball 19 due to the force of the spring 21, and the working
piston 15 gets pushed into the respective outer housing 14 or 14a, so
that the additional cam 3 is inactive. When the control piston is loaded
with a higher oil pressure, the spring 21 is compressed and the
non-return valve can close after a pressure build-up in the high pressure
chamber and a force application to the working piston, so that the
working piston is extended and the additional cam 3 is activated by the
roller 4 and effects an additional brake opening of the exhaust valve or
valves 13 and 13a.